SQL (Structured Query Language) is used to cummunicate with RDBMS (Relational database management systems). In this category you, you will find all tutorials about SQL. You can use it both as a quick-reference, and to increase your knowledge by following tutorials that catches your interest.
It can be hard to memorize even simple SELECT and INSERT statements. But once you have them memorized it is also going to make you more efficient when working with SQL.
One way towards memorization is to simply keep looking things up until you finally remember. Of course another really good way to practice, is to simply systematically try to type in commands when working with your databases.